Sewing machines which employ pattern cams for influencing the pattern of successive needle penetrations regularly employ stop motion mechanisms operated by special cam means and effective to stop the actuation of the machine upon completion of each given cycle of cam operation. With these known stop motion devices, the number of stitches which must be formed in each cycle of machine operation is proscribed and, therefore, these known devices would not be appropriate for providing single pattern control for stitch patterns of which the number of stitches may vary for each pattern. Moreover, the forces incident to the operation of the known stop motion devices for abruptly terminating the operation of the sewing machine actuating mechanism require strength and frame rigidity in excess of that which is conveniently available in the usual household sewing machine.